基于驾驶人视觉特性和停车视距的公路平面交叉角度研究

Study on Highway Intersection Angle Based on Driver’s Visual Characteristics and Stopping Sight Distance

公路平面交叉受地形限制常存在斜交情况,由于《公路路线设计规范》针对平交交角的规定不够细化,当平交斜交角度过小时,处于锐角象限的驾驶人受最大视野的限制,无法保障停车视距的要求,从而导致事故频发。为了研究平交斜交角度合理取值,采用了解析几何法建立交角计算模型。首先通过分析驾驶人在平交的动态视觉特性,基于人眼动态视野结合驾驶人头部扭转,确定了视野范围。其次从被交路驾驶人视角出发,以驾驶人视野覆盖平交视距三角形为前提条件,考虑车辆直行和左转两种情况,分别建立计算模型,求解非线性参数方程。结果表明:公路平交交角最小值与相交公路设计速度密切相关。比较两种情况下模型对应计算结果,发现当主路设计速度大于等于40 km/h,被交路车辆左转为限制平交交角最小值的主要情况,且被交路驾驶人观测到主路冲突车辆时刻的行驶速度随平交左转弯半径设计值增大而增大,但转弯半径增大不会引起平交交角最小值一定下降,这表明意图通过增大左转弯半径设计值来改善驾驶人在平交通视性是无效的,主被交路设计速度一定时,设有中间带的道路有益于改善平交通视性。当主路设计速度低于40 km/h,被交路车辆直行为限制平交交角最小值的主要情况。最后提出了基于主路设计速度的平交交叉角度建议值,以满足平交行车安全。

Highway intersections are often subject to oblique crossing angle due to terrain restrictions.As the Design Specification for Highway Alignment does not specify enough intersection angles,when the oblique crossing angle is too small,the drivers in the acute quadrant is restricted by the maximum view field,and the requirement of parking sight distance cannot be guaranteed,which may lead to frequent accidents.In order to study the reasonable value of the oblique angle of intersection,the angle calculation model is established by using the analytical geometry method.First,by analyzing the dynamic visual characteristics of the driver at intersection,the visual field is determined based on the dynamic visual field of the human eye combining with the twisting of the driver’s head twisting.Then,starting from the driver’s visual angle on the crossed road and assuming that the driver’s view field covers the sight triangle of the intersection,considering the situations of the vehicle going straight and turning left,the calculation models are established respectively to solve the nonlinear parameter equations.The result shows that the minimum value of the intersection angle is closely related to the design speed of the crossed road.Comparing the calculation results of the model in the 2 cases,it is found that when the design speed of the main road is not smaller than 40 km/h,the left-turn of the vehicle on the crossed road is the main situation that restrict the minimum intersection angle,and the driving speed at the moment when the driver observes the conflicting vehicles on the main road increases with the design value of the left-turn radius on the intersection.However,the increase of the turning radius will not cause a certain decrease in the minimum intersection angle,indicating that the intention to improve the driver’s visibility on the intersection by increasing the designed left-turn radius is invalid.The road with the middle belt is helpful to improve the drivers’visibility when the design speed of the main crossed road is constant.When the design speed of the main road is lower than 40 km/h,the main situation of restricting the minimum intersection angle is the straight driving of the vehicle on the crossed road.Finally,the recommended value of the intersection angle based on the design speed of the main road is proposed to meet the safety of vehicle driving on the intersection.